Fast recovery of ecg signal method and apparatus

ABSTRACT

Fast recovery electrocardiogram (ECG) signal method and apparatus are provided. In one embodiment, an ECG apparatus includes an input for receiving a biometric cardiogram signal, such as a Wilson Central Terminal (WCT) signal, and a combiner, such as an adder, for producing a compensated signal. An analog to digital converter provides a digitized version of the compensated signal to a processor. The processor produces an ECG reflective of the compensated signal and also outputs a digital signal corresponding to high frequency response of the digitized compensated signal to a digital to analog converter. The digital to analog converter provides an analog version of the digital signal corresponding to high frequency response of the digitized compensated signal to compensate for low response of the biometric cardiogram signal to high frequency spikes. A resultant ECG is produced by the processor having pacing signal contribution within the biometric cardiogram signal cancelled.

SUMMARY

Fast recovery electrocardiogram (ECG) signal method and apparatus areprovided. In one embodiment, an ECG apparatus includes an input forreceiving a biometric cardiogram signal of a patient and a compensationsignal combiner for selectively producing a compensated biometriccardiogram signal of the biometric cardiogram signal of the patient. Ananalog to digital converter provides a digitized version of thecompensated biometric cardiogram signal to a digital processor. Thedigital processor produces an ECG reflective of the compensatedbiometric cardiogram signal and also outputs a digital signalcorresponding to high frequency response of the digitized compensatedbiometric cardiogram signal to a digital to analog converter. Thedigital to analog converter provides an analog version of the digitalsignal corresponding to high frequency response of the digitizedcompensated biometric cardiogram signal to the compensation signalcombiner to compensate for low response of the biometric cardiogramsignal of the patient to high frequency spikes. A resultant ECG isproduced by the digital processor having pacing signal contributionwithin the biometric cardiogram signal cancelled.

Preferably, the input is configured to receive a Wilson Central Terminal(WCT) biometric cardiogram signal of a patient. Also, the compensationsignal combiner is in one embodiment an adder. The compensated biometriccardiogram signal of the biometric cardiogram signal of the patient canbe combined via an operational amplifier with an intra cardiac signal ina differential amplifier configuration as the input to the analog todigital converter. The processor can be configured to produce the ECGreflective of the compensated biometric cardiogram signal in a graphform reflecting microvolts of signal over time in tenths of seconds.

In another embodiment, a method of producing an electrocardiogram (ECG)is provided. A biometric cardiogram signal of a patient is received. Acompensated biometric cardiogram signal of the biometric cardiogramsignal of the patient is selectively produced. A digitized version ofthe compensated biometric cardiogram signal is provided to a digitalprocessor. The digital processor produces an ECG reflective of thecompensated biometric cardiogram signal and outputs a digital signalcorresponding to high frequency response of the digitized compensatedbiometric cardiogram signal to a digital to analog converter. Thedigital to analog converter providing an analog version of the digitalsignal corresponding to high frequency response of the digitizedcompensated biometric cardiogram signal that is combined with thebiometric cardiogram signal to compensate for low response of thebiometric cardiogram signal of the patient to high frequency spikes. Aresultant ECG is produced by the digital processor having pacing signalcontribution within the biometric cardiogram signal cancelled.

Preferably, a Wilson Central Terminal (WCT) biometric cardiogram signalis received as the biometric cardiogram signal of the patient. Also, theanalog version of the digital signal corresponding to high frequencyresponse of the digitized compensated biometric cardiogram signal is inone embodiment added to biometric cardiogram signal produce thecompensated biometric cardiogram signal.

The compensated biometric cardiogram signal of the biometric cardiogramsignal of the patient can be combined via an operational amplifier withan intra cardiac signal in a differential amplifier configuration as theinput to an analog to digital converter which provides the digitizedversion of the compensated biometric cardiogram signal to the digitalprocessor. The processor can produce the ECG reflective of thecompensated biometric cardiogram signal in a graph form reflectingmicrovolts of signal over time in tenths of seconds.

Other object and advantages of the invention will be apparent to thoseskilled in the art from the drawings and following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an ECG system based onconventional teachings.

FIG. 2 is a schematic illustration of an ECG system in accordance withthe teachings of the present invention.

FIGS. 3(A)-3(C) are illustrations of ECG related signals.

FIG. 4 is a flow diagram of a method of producing an electrocardiogram(ECG) in accordance with the teachings of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The present invention is related to ECG systems and methods. Theinventors have recognized that electrophysiology physicians require anenhanced ECG system that compensates for the interfering signals causedby pacing.

ECG monitoring systems that include pace pulse detection are known inthe art. For example, see U.S. Pat. No. 5,682,902 (Herleikson). Suchstandard ECG input systems utilize analog to digital signal processing.Pacing signals can be detected through the analysis of the digitalsignals. In conventional ECG systems, such as Herleikson, pace pulsesignals can be removed though replacement with a selected flat signalfor a specified or calculated time. The inventors have recognized thatelectrophysiology physicians can benefit from an enhanced ECG systemthat more accurately compensates for the interfering signals caused bypacing.

Consistent with the conventional methodology, an ECG system 10 can beconstructed, for example, to process Wilson Central Terminal (“WCT”) ECGsignals of a patient that average three active limb electrode voltagesmeasured with respect to a return ground electrode. As illustrated inFIG. 1, a WCT signal can be combined via an operational amplifier 12with an intra cardiac signal 14 in a differential amplifierconfiguration 15 as the input to an analog to digital converter 16. Thedigital output of the analog to digital converter 16 is then processedby a processor 18 in a conventional manner, such as corresponding to theprocessing taught by Herleikson, to produce an ECG corresponding to theWCT signal.

When the WCT signal includes a pacing charge, however, the ECG producedby the system 10 that uses conventional processing of the digitizedsignal, is partially skewed due to conventional processing of the pacingsignal.

The present invention provides an improved ECG system that implements adigital to analog compensation value to cancel out the pacing chargesuch that a more accurate ECG is produced. Referring to FIG. 2, anexample fast-recovery ECG input system 20 is provided that utilizes ananalog to digital converter 16 and associated processor 18 to detectpacing, similar to the system 10 of FIG. 1. However, the processor 18 ofthe FIG. 2 modified system 20 is configured to process the WCT signalafter being combined with an added DC value signal 21 that cancels outthe pacing charge when the WTC signal includes a pacing charge.

Applicants have recognized that when a pacing signal is applied, the WTCsignal will include both significant low and high frequency componentsthat arise from the electronic pacing pulse. As illustrated in FIG. 2,the WTC signal is passed through an adder 22 which adds the cancellationsignal 21 to compensate for the low response of the WTC signal to highfrequency spikes. The post-adder “compensated” WTC signal 23 is providedto the analog to digital converter 16 via the operational amplifier 12with an intra cardiac signal 14 in a differential amplifierconfiguration 15. The digital output of the analog to digital converter16 is then provided to a digital processor 18.

The digital output of the analog to digital converter 16 is processed bythe processor 18 in a conventional manner, such as corresponding to theprocessing taught by Herleikson, to produce an ECG corresponding to thecompensated WCT signal. Additionally, however, a high frequency responseof the digital signal received from the analog to digital converter 16is used by the processor 18 to create a digital compensation signal 25.The digital compensation signal 25 is passed through a digital to analogconverter 24 to provide the analog signal 21 which is added to the WTCsignal. The result of adding the cancellation signal 21 to the WTCsignal causes the processor 18 to produce an ECG having the pacingsignal contribution within the biometric cardiogram signal cancelledsince the ECG is based on the compensated WTC signal 23.

The high frequency response of the WTC signal, which is significant whenthe WTC signal includes a pacing pulse, is determined by the processor18 to produce the digital compensation signal 25 that is fed to thedigital to analog converter 24 to provide the compensation signal 21which is added to the WTC signal. Once a pacing artifact is detected bythe processor 18, a short averaging window can be used to keep thesignal always without an offset. The digital compensation signal 25input to the digital to analog converter 24 is smoothed to avoid steps.

The resultant ECG signal graphs both with and without having thecancellation signal applied are illustrated in FIGS. 3A and C. FIG. 3Areflects the WTC signal without cancellation and FIG. 3C illustrates theresultant ECG that utilizes the pace pulse cancellation of thefast-recovery ECG input system 20. For reference, FIG. 3B is providedthat reflects an ECG channel response to a pace pulse signal within theWTC signal. The graphs reflect microvolts (μVs) of signal over onesecond of time.

With reference to FIG. 4, An example method of producing the ECGdepicted in FIG. 3C is provided. In step 41, a biometric cardiogramsignal of a patient is received. In step 43, a compensated biometriccardiogram signal is produced by adding an analog compensation signal tothe biometric cardiogram signal of the patient. In step 45, a digitizedversion of the compensated biometric cardiogram signal is provided to adigital processor. In step 47, the digital processor produces an ECGreflective of the compensated biometric cardiogram signal and outputs adigital signal corresponding to high frequency response of the digitizedcompensated biometric cardiogram signal to a digital to analogconverter. In step 49, the digital to analog converter provides ananalog version of the digital signal corresponding to high frequencyresponse of the digitized compensated biometric cardiogram signal thatis combined with the biometric cardiogram signal in step 43 tocompensate for low response of the biometric cardiogram signal of thepatient to high frequency spikes whereby an ECG is produced by thedigital processor having pacing signal contribution within the biometriccardiogram signal cancelled.

All references cited in this application are incorporated by referenceherein as if fully set forth. It will be apparent to one of ordinaryskill in the art that many changes and modifications can be made to theembodiments described without departing from the spirit or scope of theinvention as set forth herein.

What is claimed is:
 1. An electrocardiogram (ECG) apparatus comprising:an input for receiving a biometric cardiogram signal of a patient; acompensation signal combiner for selectively producing a compensatedbiometric cardiogram signal of the biometric cardiogram signal of thepatient; an analog to digital converter for providing a digitizedversion of the compensated biometric cardiogram signal to a digitalprocessor; the digital processor configured to produce an ECG reflectiveof the compensated biometric cardiogram signal and to output a digitalsignal corresponding to high frequency response of the digitizedcompensated biometric cardiogram signal to a digital to analogconverter; and the digital to analog converter configured to provide ananalog version of the digital signal corresponding to high frequencyresponse of the digitized compensated biometric cardiogram signal to thecompensation signal combiner to compensate for low response of thebiometric cardiogram signal of the patient to high frequency spikeswhereby an ECG is produced by the digital processor having pacing signalcontribution within the biometric cardiogram signal cancelled.
 2. TheECG apparatus according to claim 1 wherein the input is configured toreceive a Wilson Central Terminal (WCT) biometric cardiogram signal of apatient.
 3. The ECG apparatus according to claim 2 wherein thecompensation signal combiner is an adder.
 4. The ECG apparatus accordingto claim 3 wherein the compensated biometric cardiogram signal of thebiometric cardiogram signal of the patient is combined via anoperational amplifier with an intra cardiac signal in a differentialamplifier configuration as the input to the analog to digital converter.5. The ECG apparatus according to claim 4 wherein the processor producesthe ECG reflective of the compensated biometric cardiogram signal in agraph form reflecting microvolts of signal over time in tenths ofseconds.
 6. The ECG apparatus according to claim 1 wherein thecompensation signal combiner is an adder.
 7. The ECG apparatus accordingto claim 6 wherein the compensated biometric cardiogram signal of thebiometric cardiogram signal of the patient is combined via anoperational amplifier with an intra cardiac signal in a differentialamplifier configuration as the input to the analog to digital converter.8. The ECG apparatus according to claim 7 wherein the processor producesthe ECG reflective of the compensated biometric cardiogram signal in agraph form reflecting microvolts of signal over time in tenths ofseconds.
 9. The ECG apparatus according to claim 1 wherein thecompensated biometric cardiogram signal of the biometric cardiogramsignal of the patient is combined via an operational amplifier with anintra cardiac signal in a differential amplifier configuration as theinput to the analog to digital converter.
 10. The ECG apparatusaccording to claim 9 wherein the processor produces the ECG reflectiveof the compensated biometric cardiogram signal in a graph formreflecting microvolts of signal over time in tenths of seconds.
 11. Amethod of producing an electrocardiogram (ECG) comprising: receiving abiometric cardiogram signal of a patient; selectively producing acompensated biometric cardiogram signal of the biometric cardiogramsignal of the patient; providing a digitized version of the compensatedbiometric cardiogram signal to a digital processor; the digitalprocessor producing an ECG reflective of the compensated biometriccardiogram signal and outputting a digital signal corresponding to highfrequency response of the digitized compensated biometric cardiogramsignal to a digital to analog converter; and the digital to analogconverter providing an analog version of the digital signalcorresponding to high frequency response of the digitized compensatedbiometric cardiogram signal that is combined with the biometriccardiogram signal to compensate for low response of the biometriccardiogram signal of the patient to high frequency spikes whereby an ECGis produced by the digital processor having pacing signal contributionwithin the biometric cardiogram signal cancelled.
 12. The methodaccording to claim 1 wherein a Wilson Central Terminal (WCT) biometriccardiogram signal is received as the biometric cardiogram signal of thepatient.
 13. The method according to claim 12 wherein the analog versionof the digital signal corresponding to high frequency response of thedigitized compensated biometric cardiogram signal is added to biometriccardiogram signal produce the compensated biometric cardiogram signal.14. The method according to claim 13 wherein the compensated biometriccardiogram signal of the biometric cardiogram signal of the patient iscombined via an operational amplifier with an intra cardiac signal in adifferential amplifier configuration as the input to an analog todigital converter which provides the digitized version of thecompensated biometric cardiogram signal to the digital processor. 15.The method according to claim 14 wherein the processor produces the ECGreflective of the compensated biometric cardiogram signal in a graphform reflecting microvolts of signal over time in tenths of seconds. 16.The method according to claim 11 wherein the analog version of thedigital signal corresponding to high frequency response of the digitizedcompensated biometric cardiogram signal is added to biometric cardiogramsignal produce the compensated biometric cardiogram signal.
 17. Themethod according to claim 16 wherein the compensated biometriccardiogram signal of the biometric cardiogram signal of the patient iscombined via an operational amplifier with an intra cardiac signal in adifferential amplifier configuration as the input to an analog todigital converter which provides the digitized version of thecompensated biometric cardiogram signal to the digital processor. 18.The method according to claim 17 wherein the processor produces the ECGreflective of the compensated biometric cardiogram signal in a graphform reflecting microvolts of signal over time in tenths of seconds. 19.The method according to claim 11 wherein the compensated biometriccardiogram signal of the biometric cardiogram signal of the patient iscombined via an operational amplifier with an intra cardiac signal in adifferential amplifier configuration as the input to an analog todigital converter which provides the digitized version of thecompensated biometric cardiogram signal to the digital processor. 20.The method according to claim 19 wherein the processor produces the ECGreflective of the compensated biometric cardiogram signal in a graphform reflecting microvolts of signal over time in tenths of seconds.